1. Field of the Invention
The present invention relates to a tool to be attached to a spindle of a machine tool for machining a workpiece.
2. Description of the Related Art
In, for example, a machining center or other machine tool provided with a spindle, the maximum rotational speed of the spindle (per unit time) is determined by the structure of a main bearing rotatably supporting the spindle and a lubrication system. For this reason, when rotation of a tool at a higher rotational speed than the maximum rotational speed of the spindle is desired, an accelerating apparatus is used.
An accelerating apparatus which holds the tool and is able to be attached to the spindle and which can increase the rotary force of the spindle by a gear mechanism such as epicyclic gearing to increase the rotational speed of the tool is known.
For example, in a machining center, when it is desired to increase the rotational speed of the tool to higher than the maximum speed of the spindle temporarily, such an accelerating apparatus is attached to the spindle in the same way as an ordinary tool to enable the tool to be rotated at a higher rotational speed.
However, when raising the rotational speed of the tool to a higher speed than the spindle by the above gear mechanism such as at a super high rotational speed such as tens of thousands to hundreds of thousands of revolutions per minute, the accelerating apparatus increasingly generates heat so the machining tolerance of a workpiece can be influenced by the heat. Further, at the above super high rotational speed, the noise from the accelerating apparatus can also increase. Furthermore, a highly reliable precision structure able to withstand the above super high rotational speed is required for the accelerating apparatus. Therefore, there is the disadvantage that the manufacturing cost becomes relatively high.
Further, in a case of an accelerating apparatus with a gear mechanism, it is necessary to lubricate the gear or bearing and arrange a supply passage and a discharge passage for the lubricating oil in the accelerating apparatus, so there is the disadvantage that the apparatus becomes larger and it is difficult to automatically change the tool by an automatic tool changer.
Further, as another accelerating method, sometimes the method is adopted of using a high frequency motor for the motor driving the tool and supplying drive current to this high frequency motor from a specially provided control apparatus so as to rotate the tool at a high speed. With this method, however, since there is a cable for supplying electric power from the outside, there are the disadvantages that it is difficult to automatically change tools like with an ordinary tool and the cost of the facilities is relatively high.
An object of the present invention is to provide a tool and a tool holder able to be attached to a spindle of a machine tool by an automatic tool changer in the same way as an ordinary tool, capable of operating without connection with an external power supply etc., and enabling tool rotation at a different rotational speed than that of the spindle of the machine tool without supplying electric power from the outside.
Another object of the present invention is to provide a machine tool not requiring the supply of electric power to an attachment using electric power attached to the machine tool body from an external power supply through a power feed cable.
Another object of the present invention is to provide a machine tool provided with the above tool and tool holder.
According to a first aspect of the present invention, there is provided a tool attachable to a spindle of a machine tool comprising a machining tool for machining a workpiece; a motor connected to the machining tool and causing the machining tool to rotate; and a generator to which rotary force is transmitted from a spindle of the machine tool and generating electric power to drive the motor; wherein a shaft of the motor is arranged in an orientation different from an axial center of the spindle.
Preferably, the tool is provided with a plurality of the motors and machining tools.
Preferably, the tool further comprises an attachment part attachable to the spindle and transmitting rotary force of the spindle to the motor and a case for holding the motor and generator, rotatably holding the attachment part, and engaging with a non-rotating portion of the machine tool so as to be restricted from rotation.
Preferably, the generator is an alternating current generator which supplies voltage of a frequency in accordance with the rotational speed of the spindle to the motor, and the motor is an induction motor rotating by the rotational speed in accordance with a frequency.
According to a second aspect of the invention, there is provided a tool holder able to hold a machining tool for machining a workpiece and attachable to a spindle of a machine tool body, comprising a tool holding part for rotatably holding the machining tool; a motor for rotating the tool holding part; and a generator to which rotary force is transmitted from a spindle of the machine tool and generating electric power to drive the motor; wherein a shaft of the motor is arranged in an orientation different from an axial center of the spindle.
Preferably, the tool holder is provided with a plurality of the motors and tool holding parts.
According to a third aspect of the present invention, there is provided a machine tool comprising a machine tool body provided with a spindle, a driving means for driving the spindle, and at least one control axis for changing a relative position between the spindle and a workpiece; a control apparatus for controlling the driving means and the control axis in accordance with a machining program; and an automatic tool changer provided with a plurality of types of tools and attaching a tool to the spindle; the plurality of types of tools each including a machining tool for machining a workpiece, a motor connected to the machining tool and rotating the machining tool, and a generator to which rotary force is transmitted from the spindle and generating electric power to drive the motor.
Preferably, the tools include a plurality of tools having different postures of shafts of the motors with respect to axial centers of the spindle.
Alternatively, the tools include tools provided with a plurality of motors and machining tools.
According to a fourth aspect of the present invention, there is provided a machine tool comprising a generator for generating electric power by power supplied from the outside and an electrodischarge machining electrode for performing electrodischarge machining using the electric power generated by the generator.
Preferably, the tool further comprises an attachment part able to be attached to a moving and positioning means for moving and positioning the electrodischarge machining electrode with respect to a workpiece to be machined by electrodischarge machining.
Alternatively, the tool further comprises an electrode holding means for exchangeably holding the electrodischarge machining electrode.
More preferably, the moving and positioning means is a machine tool able to cut a workpiece, and the generator generates electric power by power from a power source provided in the machine tool.
Still more preferably, the generator generates electric power by the transmission of rotary force of the spindle of the machine tool.
According to a fifth aspect of the present invention, there is provided an electrodischarge electrode holder comprising a generator for generating electric power by power supplied from the outside and a holding means for exchangeably holding an electrodischarge machining electrode for electrodischarge machining using electric power generated by the generator.
Preferably, the holder further comprises an attachment part able to be attached to a moving and positioning means for moving and positioning the electrodischarge machining electrode with respect to a workpiece to be machined by electrodischarge machining.
According to a sixth aspect of the present invention, there is provided a machine tool able to cut a workpiece, comprising a machine tool body moving and positioning a spindle with respect to a workpiece; a tool provided with a generator and an electrodischarge machining electrode for electrodischarge machining using electric power generated by the generator and able to be attached to the machine tool body; and a power source for supplying power to the generator.
Preferably, the power source is a drive motor for rotating the spindle.
According to a seventh aspect of the present invention, there is provided a tool able to be attached to a spindle of a machine tool, comprising a machining tool for machining a workpiece; a generator for generating electric power by rotary force supplied from the spindle of the machine tool; a motor drive by electric power generated by the generator and rotating the machining tool; and a cooling means for discharging to the outside heat generated by the operation of the motor using part of the electric power generated by the generator.
Preferably, the cooling means has a Peltier element.
According to an eighth aspect of the present invention, there is provided a tool holder able to hold a machining tool for machining a workpiece and able to be attached to a spindle of a machine tool body, comprising a tool holding part for rotatably holding the machining tool; a generator for generating electric power by rotary force supplied from the spindle of the machine tool; a motor drive by electric power generated by the generator and rotating the machining tool; and a cooling means for discharging to the outside heat generated by the operation of the motor using part of the electric power generated by the generator.
Preferably, the cooling means has a Peltier element.
According to a ninth aspect of the present invention, there is provided a machine tool comprising a machine tool body provided with a spindle, a drive means for driving the spindle, and at least one control axis for changing a relative position between the spindle and the work; a tool provided with a machining tool for machining a workpiece, a generator for generating electric power by rotary force supplied from the spindle of the machine tool, and a motor driven by electric power generated by the generator and rotating the machining tool and able to be attached to the spindle; and a control apparatus for controlling the drive of the drive means and the control axis in accordance with a machining program; the tool further having a cooling means for discharging to the outside heat generated by the operation of the motor using part of the electric power generated by the generator.
According to a 10th aspect of the present invention, there is provided a machine tool comprising a machine tool body; a power source provided at the machine tool body and supplying power required for machining the workpiece; a generator for generating electric power using part of the power supplied from the power source; and an attachment for the machine tool body using power generated by the generator.
Preferably, the attachment is provided with a motor driven using electric power generated by the generator and is attached to the machine tool body.
More preferably, the machine tool further comprises a connecting means for electrically connecting the generator and the motor by being attached in the machine tool body.
Preferably, the power source is a drive motor for driving a spindle rotatably held in a spindle housing of the machine tool body, and the generator is built into the spindle housing and generates electric power by rotation of the spindle.
More preferably, the attachment is rotated by said motor and has a tool for machining work.
In the first to third aspects of the present invention, a tool able to be attached to a spindle is provided with a generator and a motor, electric power is generated using the rotary force of the spindle, and the motor is operated by the generated electric power to rotate the machining tool. Due to this, the tool can be driven without connection to an external power supply etc., and automatic tool changing also becomes possible.
Further, it is possible to deal with various types of machining by providing various types of tools with different postures and numbers of motors in an automatic tool changer in advance.
In the fourth to sixth aspects of the present invention, a generator generates electric power by power supplied from the outside. By supplying the generated electric power to an electrodischarge machining electrode, electrodischarge machining becomes possible. By attaching this tool to for example a machine tool body or other moving and positioning means and moving and positioning the tool with respect to a workpiece, a workpiece can be machined by electrodischarge machining.
In the seventh to ninth aspects of the present invention, a tool able to be attached to a spindle is provided with a generator and a motor, electric power is generated using the rotary force of the spindle, and the motor is operated by the generated electric power to rotate the machining tool. Due to this, the tool can be driven without connection to an external power supply etc., and automatic tool changing also becomes possible.
The tool of the seventh aspect of the invention is completely independent from the spindle and any external apparatus, but generates heat when the motor is driven. Therefore, a cooling means is provided at the tool, and part of the electric power generated by the generator is used to discharge the heat generated by the operation of the motor. Due to this, it is possible to avoid the effects of heat generated by the operation of the motor and possible to maintain the properties of the tool of the present invention without requiring connection with the outside etc.
In the 10th aspect of the present invention, part of the power from a power source is supplied to a generator, whereupon the generator generates electric power. The power generated by this generator is used by an attachment. For example, when the attachment is provided with a motor, the motor is driven. By attaching the attachment with the built-in motor to a spindle housing of a machine tool body and rotating the tool by this motor, the workpiece can be cut by a tool rotating independently from the rotation of the spindle.